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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

240

SPECIAL BRONZES

on a sand-bath with 3-4 c.c. of cone, sulphuric acid until white fumes of
sulphuric acid appear. The lead is determined as sulphate in the way
given for the gravimetric analysis of ordinary brasses.

3.  Determination of the Copper,  Iron,  Nickel   and  Zinc.—(«)
ELECTROLYTICALLY.   The liquid freed from lead is evaporated until the
alcohol is expelled and the residual liquid mixed with 20 c.c. of nitric acid
and electrolysed as in the case of argentan.

(6) GRAVIMETRICALLY. The liquid freed from lead is evaporated to
eliminate the alcohol, mixed with 200-250 c.c. of water, heated to boiling
and the copper precipitated with hydrogen sulphide, the subsequent pro-
cedure being that described for the gravimetric analysis of argentan.

4.  Determination of the Phosphorus,  Arsenic  and  Sulphur.—
See Ordinary Bronzes.

*
* *

Lead-rdckel-bronzes have the following mean composition :   64% Cu, 30%
Pb, 5% Sn, and i% Ni.

Aluminium -bronzes

Aluminium-bronzes have a fine, golden-yellow colour and are used for
making vases, ornamental articles, etc. They consist essentially of copper
and aluminium (3-10%) and often contain small quantities of silicon and
iron. Their analysis includes :

1.  Determination   of the  Silicon.—I gram of  the alloy is   heated
gently with 10 c.c. of nitric acid (D 1-2) and the solution evaporated with
10 c.c. of 50% sulphuric acid until white fumes of sulphuric acid appear.
The residual liquid is mixed with 30 c.c. of water, heated for some time and,
when cold, filtered through a small filter ; the residue of more or less pure
silica is washed, dried, calcined in a platinum crucible and weighed.    It is
then treated with hydrofluoric acid, etc., as in the determination of silicon
in iron.

2.  Determination of the Copper.—The filtrate is treated with 4-5
c.c. of nitric acid, diluted to about 150 c.c. and subjected to electrolysis
(see Electrolytic Determination of Copper in Ordinary Brasses).

3.  Determination  of the  Iron  and  Aluminium.—After removal
of the copper, the liquid is rendered alkaline with ammonia, boiled for some
time and the precipitated aluminium and ferric hydroxides filtered off,
washed, calcined and weighed.   The oxides are then fused with potassium
bisulphate, the residue taken up in dilute sulphuric acid and the iron in
the solution determined electrolytically or volumetrically.    The iron and
aluminium are thus obtained separately.

*
* *

The compositions of the more important industrial types of aluminium-
bronzes are as follows (Guillet) :rus.